Insight into the comparison of key aroma-active compounds between camellia oils from different processing technology

Comparison of extraction and refinement techniques for volatile compound analysis in camellia oil

The processing techniques of camellia oil, containing freshly squeezed (FSCO), refined (DFCO), cold-pressed (OFCO), and hot-pressed (RFCO), significantly influence flavor compounds and organoleptic properties. In this study, the preference for FSCO and RFCO was revealed by sensory evaluation due to the "fruity" and "roasted" flavors, respectively. Flavor differences among oils were accurately distinguished by the E-nose. A total of 77 and 116 odorants were identified by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and gas chromatography-mass spectrometry (GC-MS), respectively. The gas chromatography-olfactometry (GC-O) and detection frequency analysis identified 34 active-aroma compounds with DF ≥ 2. Aroma recombination and omission experiments further confirmed that (E)-2-nonenal and nonanal, derived from the degradation of unsaturated fatty acids, significantly contributed to "green" and "fruity" aromas. Notably, these concentrations positively correlated with sensory preference. This study provides valuable insights into the flavor identification of camellia oil and the improvement of processing techniques.

Volatile profiles and characteristic odorants in camellia seeds with different heat pretreatments

Heat pretreatment plays a crucial role in affecting the quality, colour and aroma of camellia oil during the extraction process. This study aimed to investigate the effects of steaming, stir-frying, roasting, microwave and infrared treatment on the flavour and physicochemical quality of camellia seeds. The results indicated that, compared with unpretreated samples, the heat-pretreated ones exhibited increased oil content and browning degree, imparting a caramel colour with toasty and nutty flavours. 137 VOCs, including 23 characteristic aroma compounds, were detected by HS-SPME/GC-O-MS analysis. 17 different VOCs were identified by OPLS-DA and 12 key aroma compounds (KACs) were determined by ROAV. Moreover, 6 characteristic flavour substances were obtained through comprehensive analysis. The relationship between physicochemical properties and sensory attributes was elucidated using the Mantel test. This study provided scientific insights into the formation mechanism of camellia seeds flavour and supported further development of processing strategies to enhance camellia seeds flavour.

Effect of moisture loss on aroma profile, key odorants, and fatty acids of Amomum tsaoko during vacuum oven drying

The effects of vacuum oven drying at 60 °C on the aroma profile, key odorants, fatty acids, and chiral compounds of fresh Amomum tsaoko (AT) were evaluated over varying drying times. Quantitative descriptive analysis, solvent-assisted flavor evaporation, and gas chromatography-olfactometry-mass spectrometry identified and quantitated 36 odor-active compounds. Aldehydes, particularly geranial (1606-1809 mg/kg), were consistently prominent across all drying durations. Twenty-four key odorants with odor activity values greater than one were identified and screened. Relationships among seven samples, 24 key odorants, and six attributes were elucidated through orthogonal partial least squares-discriminant analysis. Notably, 13 odorants exhibited changes during the drying process, as indicated by variable importance for projection scores. Additionally, fatty acid analyses revealed that palmitic and oleic acids were predominant in AT. This study provides valuable insights into the impact of moisture loss on the key chemical components of AT, supporting the development of diverse consumer-oriented products.

Investigation on sweaty off-flavors in small mill sesame oil and its formation mechanism via molecular sensory science, preparative gas chromatography, and microbiomics

The distinctive and enjoyable aroma of small mill sesame oil (SMSO) originates from the aqueous extraction process. However, in the sedimentation stage in industrial production, when the external ambient temperature is elevated, unpleasant sweaty off-flavors may be present from an unknown source. Based on the odor screening and verification strategy, 76 volatile flavor compounds were identified in different SMSOs, and 3 key areas had a sweaty odor via gas chromatography olfactometry (GC-O) analysis. The validation experiment utilizing preparative gas chromatography (pre-GC) confirmed the sweaty off-flavors were butyric acid, 2-methylbutyric acid, and isobutyric acid, with odor activity values ranging from 1 to 100. Furthermore, microbiological investigations on sesame residues gathered during the sedimentation process at various temperatures revealed sweaty off-flavors were mostly attributed to the collaborative interaction of Lactobacillus, Yarrowia lipolytica, and butanoate 1-phosphotransferase. This study offers a fundamental theoretical foundation for enhancing the quality control and flavor of SMSO.

Characterizing and decoding the key odor compounds of Spirulina platensis at different processing stages by sensomics

Processing is an indispensable technology in the preparation of Spirulina platensis (S. platensis). The key odorants in liquids, muds, and powders from S. platensis (NM and GZ) were characterized. A total of 90 odorants were identified and 41 odorants were sniffed with the flavor dilution (FD) factors ranging from 1 to 729. Among them, nonanal, decanal, d-limonene, β-cyclocitral, and β-ionone with FD factors ≥1 were detected in S. platensis during the whole processing stages. In addition, heptanal, (E, E)-2,4-nonadienal, trans-4,5-epoxy-(E)-2-decenal, 1-hepten-3-one, isophorone, 3-ethyl-2,5-dimethylpyrazine, and α-ionone exhibited higher odor activity values in powders; β-myrcene, methional, and S-methyl methanethiosulphonate were key odorants in muds; while trans-3-penten-2-ol was key odorant in liquids. Besides, the GZ-mud presented stronger earthy and fishy odor than NM-mud. S. platensis powders have the stronger grassy odor, roasted odor, and marine odor than S. platensis muds. Overall, drying process promotes the formation of aldehydes, heterocyclic compounds, and terpenoids.

Unlocking aroma in three types of vinasse fish by sensomics approach

Vinasse fish (VF), a traditional Chinese food, is unique in flavor. However, the key aroma compounds influencing consumer acceptance of VF remain unclear. In this study, the key aroma compounds in three types of VF were explored by a sensomics approach. The results indicated that a total of 50 aroma compounds were quantified, of which 22 compounds exhibited odor activity values ≥1 were key aroma contributors. Eleven key aroma compounds were further confirmed by recombination and omission experiments. Ethyl hexanoate, 1-octen-3-one, and trans-anethole were mutual key aromas, while eugenol, ethyl heptanoate, (2E)-2-nonenal, and hexanal were distinct aroma markers. Particularly, ethyl heptanoate, γ-nonalactone, and eugenol were newly identified as key aroma compounds in VF. Overall, this study revealed the key aroma compounds and their differences in three types of vinasse fish, which will provide profound insights for comprehensively exploring the formation and target regulation of unique flavor in vinasse fish.

Comprehensive analysis of the effects of the traditional stir-fry process on the dynamic changes of volatile metabolites in Hainan camellia oil

The traditional stir-fry process before pressing is crucial to manufacture Hainan camellia oil. To assess the effects of the stir-fry process on Hainan camellia oil, six samples across different stir-fry stages were analyzed. The stir-fry process modified odors, volatile metabolite profiles, and human health-promoting functions of Hainan camellia oil. Totally, 350 volatile metabolites were detected, and heterocyclic compounds were revealed as the main contributors of strong aroma. Potential indicators for monitoring the stir-fry degree were established. Eight key aroma volatile metabolites were identified, including three new ones (1-octen-3-one, 2,3-butanedione, and vanillin). Lipids degradation and the Millard reaction are probably the main pathways for aroma generation. Over-stir-fry treatment diminished the contents of some important volatile metabolites but increased the risk of arising burnt odor. Our work offered insights into the effects of the stir-fry process and over-stir-fry treatment on Hainan camellia oil, which is meaningful for improving the hot-pressing technique.

Comparison evaluation pretreatments on the quality characteristics, oxidative stability, and volatile flavor of walnut oil

In this study, we applied various thermal pretreatment methods (e.g., hot-air, microwave, and stir-frying) to process walnut kernels, and conducted comparative analysis of the physicochemical properties, nutritional components, in vitro antioxidant activity, and flavor substances of the extracted walnut oil (WO). The results indicated that, thermal pretreatment significantly increased the extraction of total trace nutrients (e.g., total phenols, tocopherols, and phytosterols) in WO. The WO produced using microwave had 2316.71 mg/kg of total trace nutrients, closely followed by the stir-frying method, which yielded an 11.22% increase compared to the untreated method. The WO obtained by the microwave method had a higher Oxidative inductance period (4.05 h) and oil yield (2.48%). After analyzing the flavor in WO, we found that aldehydes accounted for 28.77% of the 73 of volatile compounds and 58.12% of the total flavor compound content in microwave-pretreated WO, these percentages were higher than those recorded by using other methods. Based on the comprehensive score obtained by the PCA, microwave-pretreatment might be a promising strategy to improve the quality of WO based on aromatic characteristics.

The effect of extraction methods on the components and quality of Camellia oleifera oil: Focusing on the flavor and lipidomics

The objective of this study was to systematically elucidate the effects of conventional (Cold Pressing, CP; Hot Pressing, HP; Soxhlet Extraction; SE) and novel methods (Microwave-Assisted Extraction, MAE) on the physicochemical properties, bio-active substances, flavor and lipidomics of Camellia oleifera oil (COO). The cold-pressed COO contained the highest contents of squalene (176.38 mg/kg), α-tocopherol (330.52 mg/kg), polyphenols (68.33 mg/kg) and phytosterols (2782.55 mg/kg). Oleic acid was observed as the predominant fatty acid with the content of approximately 80%. HS-GC-IMS identified 47 volatile compounds, including 11 aldehydes, 11 ketones, 11 alcohols, 2 acids, 8 esters, 2 pyrazines, 1 furan, and 1 thiophene. A total of 5 lipid classes and 30 lipid subclasses of 339 lipids were identifed, among which TGs and DGs were observed as the major lipids. In summary, both cold-pressed and microwave-assisted technologies provided high-quality COO with high content of bio-active substances and diglycerides/triglycerides.